1. Field of the Invention
The present invention relates to motor-driven compressors used in vehicle air conditioning systems to compress refrigerant, and more particularly, to motor-driven compressors having a motor driven by a power supply, such as a battery.
2. Description of Related Art
Motor-driven compressors are known in the art. For example, Japanese Unexamined Patent Publication No. 2000-291557 describes a motor-driven compressor formed with a housing containing a compression portion and a motor for driving the compression portion to compress refrigerant. In this known motor-driven compressor, a drive circuit for controlling the operation of the motor is disposed adjacent to a suction port for refrigerant gas. In the drive circuit, a capacitor is included as one of the components of an inverter. The capacitor is provided to smooth, i.e., to reduce or eliminate, the alternating current component or ripple current of current supplied from a direct-current (DC) power supply to the motor. According to this known motor-driven compressor, a cooling device, such as a radiator, fan, water cooling radiator or water circulating pipes, is no longer necessary for cooling the drive circuit.
In the known motor-driven compressor, however, a high-frequency, ripple current flows through the capacitor, thereby increasing the heat generated in the capacitor. Moreover, the increase in heat generated in the capacitor by the ripple current may require an increase in the size of a capacitor used to handle the increased heat generated by such high-frequency, ripple current. The increased size of the capacitor may increase the cost of the capacitor. In addition, because the drive circuit may be manufactured separately and attached to the motor-driven compressor, the capacitor may extend from a housing of the motor-driven compressor. As a result, the size of the known motor-driven compressor with a built-in inverter may increase due to any increase in the size of the capacitor.
A need has arisen in motor-driven compressors that use capacitors for smoothing current supplied to the motor, to reduce the overall size of the motors. Further needs have arisen to reduce the manufacturing cost of such motor-driven compressors and to facilitate heat transfer from the capacitors.
In an embodiment of this invention, a motor-driven compressor comprises a housing containing a compression portion and a motor for driving the compression portion to compress refrigerant. The compressor housing further comprises a suction housing for introducing the refrigerant. A capacitor is provided for smoothing current supplied from a power source to the motor. The capacitor is disposed in contact with the suction housing. In further embodiments of this invention, the capacitor may be disposed on various portions of the suction housing and in one of a plurality of orientations relative to an axial direction of the motor-driven compressor. The selected orientations facilitate heat transfer and reduce the overall dimensions of the motor-driven compressor.